Typical CMOS silicon array photosensors have an array of photosensor cells, each cell including at least one photodiode and at least one transistor. The at least one transistor arranged to select photodiode, reset the photodiode by charging it to a “dark” level, and to sense charge on the photodiode after the photodiode has been exposed to light. There are several different physical and circuit arrangements of the transistors in cells known in the art.
Exposure of the photodiode to light alters charge on the photodiode from the “dark” level to a level that is a function of the amount of light to which the photodiode is exposed. Dark current of a photodiode is a leakage current in each photodiode that also alters charge on the photodiode in similar manner to the way light alters charge on the photodiode.
Most prior silicon array photosensors are built in [100] single-crystal substrates. Some of these photosensors have isolation trenches to limit crosstalk and leakage between adjacent photosensors of the array; crosstalk and leakage may result in blooming of images having intensely lit areas near dark areas. Embodiments disclosed herein pertain to isolation trenches in silicon substrates used with such array photosensors, and fabrication methods thereof.